Drug Monograph
Fentanyl
fentanyl citrate — Sublimaze (injection), Duragesic (transdermal patch)
Pharmacokinetic Profile
Half-Life
IV: ~3.7 h (219 min); Transdermal: 17 h (13–22 h) apparent after patch removal
Metabolism
Hepatic via CYP3A4 to norfentanyl (inactive)
Protein Binding
80–85% (alpha-1-acid glycoprotein, albumin)
Bioavailability
Transdermal ~92%; IV 100%
Volume of Distribution
4 L/kg
Clinical Information
Drug Class
Full mu-opioid agonist (synthetic phenylpiperidine)
Potency
50–100x morphine
Available Doses
Injection: 50 mcg/mL; Patches: 12, 25, 50, 75, 100 mcg/h
Route
IV, IM, transdermal, epidural, intrathecal
Renal Adjustment
Caution; clearance may decrease
Hepatic Adjustment
Reduce dose; monitor closely
Pregnancy
Avoid prolonged use; NOWS risk
Lactation
Excreted in breast milk; not recommended (transdermal)
Schedule
DEA Schedule II
Generic Available
Yes (injection and transdermal)
Black Box Warning
Yes — multiple (incl. CYP3A4)
Therapeutic Index
Very narrow
Indications
| Indication | Approved Population | Therapy Type | Status |
|---|---|---|---|
| Analgesic supplement in general or regional anaesthesia | Adults | Adjunctive to anaesthetic agents | FDA Approved |
| Analgesic action of short duration during anaesthetic periods — premedication, induction, maintenance | Adults | Monotherapy or adjunctive | FDA Approved |
| Primary anaesthetic agent for major surgery requiring open-heart procedures or complex neurological/orthopaedic procedures | Adults | High-dose monotherapy with oxygen and neuromuscular blocker | FDA Approved |
| Chronic pain requiring continuous around-the-clock opioid (transdermal patch) | Opioid-tolerant adults; opioid-tolerant children ≥2 y | Monotherapy | FDA Approved |
Fentanyl is a highly potent synthetic opioid with rapid onset and short duration of action when given intravenously, making it a cornerstone of perioperative pain management and anaesthesia. The injectable formulation should only be administered by personnel trained in airway management and equipped with resuscitation equipment. The transdermal formulation delivers fentanyl continuously over 72 hours and is exclusively indicated for opioid-tolerant patients with severe chronic pain. Opioid tolerance is defined as receiving at least 60 mg oral morphine daily, 25 mcg/h transdermal fentanyl, 30 mg oral oxycodone daily, 8 mg oral hydromorphone daily, or an equianalgesic dose of another opioid for one week or longer (FDA PI).
Off-Label Uses
Procedural sedation/analgesia (emergency department, interventional radiology) — Low-dose IV fentanyl (0.5–1 mcg/kg) is widely used for procedural pain and sedation. Evidence quality: High.
Intrathecal/epidural labour analgesia — Fentanyl 15–25 mcg is commonly added to neuraxial local anaesthetics for combined spinal-epidural technique. Evidence quality: High.
Refractory dyspnoea in palliative care — Nebulised or low-dose parenteral fentanyl is used for breathlessness in terminal illness. Evidence quality: Moderate.
Dosing
Injectable Fentanyl — By Clinical Scenario
| Clinical Scenario | Starting Dose | Maintenance Dose | Maximum Dose | Notes |
|---|---|---|---|---|
| Minor surgery — analgesic supplement | 50–100 mcg IV/IM | 25 mcg IV increments PRN | 2 mcg/kg total | Onset 1–2 min IV; duration 30–60 min Adjunct to regional anaesthesia or premedication 30–60 min before surgery |
| Major surgery — moderate dose | 2–20 mcg/kg IV | 25–100 mcg IV PRN | 20 mcg/kg total | Administered with N2O/O2 ± volatile agent Higher doses within range increase risk of muscle rigidity requiring NMB; expect respiratory depression requiring assisted ventilation |
| Cardiac anaesthesia — high dose | 20–50 mcg/kg IV | 25 mcg to half initial dose PRN | Up to 150 mcg/kg | Used with O2 + NMB; postoperative ventilation expected Provides haemodynamic stability; minimize volatile agent exposure |
| Postoperative pain — IV/IM bolus | 50–100 mcg IV/IM | 50–100 mcg q1–2h PRN | Individual | Monitor respiratory status closely in recovery Respiratory depression may outlast analgesic effect; may also be used for tachypnoea and emergence delirium (FDA PI) |
| Postoperative pain — IV PCA | 10–20 mcg demand dose | 10–25 mcg demand | Institutional protocol | Lockout interval 5–10 min; basal infusion generally not recommended in opioid-naive 1-hour limit typically 100–200 mcg |
| ICU sedation/analgesia — infusion | 25–50 mcg IV bolus, then 25–100 mcg/h | 25–200 mcg/h | Titrate to target sedation | Titrate to validated scale (RASS, CPOT); accumulation with prolonged infusions Context-sensitive half-time increases significantly after >2 h infusion |
| Procedural sedation (ED/radiology) | 0.5–1 mcg/kg IV | 0.5 mcg/kg q3–5 min PRN | 3–5 mcg/kg total | Combine with midazolam or propofol per protocol Monitor SpO2 continuously; capnography recommended |
| Neuraxial — epidural analgesia | 50–100 mcg bolus | 25–100 mcg/h infusion (with LA) | Individual | High lipophilicity limits rostral spread; rapid onset (5–10 min) Typically combined with bupivacaine 0.0625–0.125% |
Transdermal Fentanyl — Chronic Pain (Opioid-Tolerant Only)
| Clinical Scenario | Starting Dose | Maintenance Dose | Maximum Dose | Notes |
|---|---|---|---|---|
| Chronic cancer pain — conversion from oral morphine | 25 mcg/h patch q72h | Titrate q72h by 12–25 mcg/h | Individual (no ceiling for cancer) | Use equianalgesic table: 60–134 mg oral morphine/day ≈ 25 mcg/h patch Up to 24 h for initial therapeutic effect; provide IR opioid for breakthrough |
| Chronic non-cancer pain — opioid-tolerant | Lowest appropriate dose | Titrate q72h by 12–25 mcg/h | Lowest effective dose | Re-evaluate ongoing necessity regularly; CDC recommends caution >90 MME/day Avoid in acute or intermittent pain settings |
| Paediatric — opioid-tolerant children ≥2 years | Based on equianalgesic conversion | Titrate cautiously | Individual | 30–44 mg oral morphine/day ≈ 12 mcg/h patch; children metabolise fentanyl faster Only for children already receiving ≥60 mg oral morphine equivalent/day for ≥1 week |
Special Population Adjustments
| Clinical Scenario | Starting Dose | Maintenance Dose | Maximum Dose | Notes |
|---|---|---|---|---|
| Hepatic impairment | Reduce by 50% | Titrate cautiously | Reduce proportionally | Clearance may be decreased; monitor for prolonged/increased effect Transdermal: not recommended in severe hepatic impairment (FDA PI) |
| Renal impairment | Reduce initial dose | Titrate cautiously | Reduce proportionally | Fentanyl not dialysable; lower clearance in ESRD Transdermal: not recommended in severe renal impairment (FDA PI) |
| Elderly (≥65 years) | Reduce starting dose by 50% | Titrate slowly | Individual | Greater sensitivity to respiratory depression; t½ may be prolonged to ~34 h (transdermal) Start with lowest available patch strength if converting |
Clinical Pearl — Context-Sensitive Half-Time
Fentanyl has a short terminal elimination half-life (~3.7 h) after a single IV dose. However, with prolonged infusions (>2 hours), fentanyl accumulates in fat and muscle compartments, and the context-sensitive half-time (time for plasma concentration to fall 50% after stopping the infusion) increases dramatically. After a 4-hour infusion, the context-sensitive half-time is approximately 200 minutes compared to minutes after a single bolus. This is clinically critical in ICU settings where fentanyl infusions may run for days, resulting in prolonged sedation after discontinuation (FDA PI).
Critical Safety: Transdermal Patch and Heat Exposure
External heat sources (heating pads, electric blankets, saunas, hot tubs, fever) can increase fentanyl absorption from the patch by approximately one-third, potentially causing fatal overdose. Patients must avoid heat exposure to the patch application site. Fever (≥40°C) requires close monitoring and possible dose reduction (FDA PI).
Pharmacology
Mechanism of Action
Fentanyl is a fully synthetic phenylpiperidine opioid that binds with high affinity to the mu-opioid receptor (MOR). Its extreme potency (50–100 times morphine) stems from its high lipophilicity and strong receptor binding affinity, enabling rapid penetration of the blood-brain barrier. At the MOR, fentanyl activates inhibitory G-proteins that suppress adenylyl cyclase activity, open potassium channels, and close voltage-gated calcium channels in dorsal horn neurons, resulting in diminished nociceptive signal transmission. Supraspinally, it modulates descending inhibitory circuits from the periaqueductal grey and the rostral ventromedial medulla. Fentanyl also depresses the medullary respiratory centre by reducing sensitivity to CO2 — this respiratory depressant effect may outlast its analgesic action. Unlike morphine, fentanyl causes minimal histamine release, which contributes to greater haemodynamic stability during anaesthesia. At higher doses, fentanyl may cause skeletal muscle rigidity (particularly truncal rigidity), a phenomenon that can impair ventilation and requires neuromuscular blockade.
ADME Profile
| Parameter | Value | Clinical Implication |
|---|---|---|
| Absorption | IV onset 1–2 min, peak 3–5 min; transdermal: therapeutic levels in 12–24 h, steady state by end of second patch; bioavailability ~92% transdermal, 100% IV | Transdermal bypasses first-pass metabolism; up to 24 h to reach therapeutic levels — always provide immediate-release opioid for the first 12–24 h of initial patch application |
| Distribution | Vd 4 L/kg; protein binding 80–85% (alpha-1-acid glycoprotein); highly lipophilic; accumulates in skeletal muscle and fat; distribution time 1.7 min, redistribution 13 min | High lipophilicity enables rapid CNS penetration (onset <1 min IV) but also extensive tissue accumulation; context-sensitive half-time increases with prolonged infusion; pH-dependent protein binding affects distribution |
| Metabolism | Hepatic and intestinal mucosal metabolism via CYP3A4 to norfentanyl (primary, inactive metabolite); no active metabolites | CYP3A4 is the critical drug interaction pathway — potent CYP3A4 inhibitors (ritonavir, ketoconazole, clarithromycin) can cause fatal accumulation; CYP3A4 inducers (rifampin, carbamazepine) may reduce efficacy or precipitate withdrawal |
| Elimination | t½ 219 min (~3.7 h) IV terminal; transdermal apparent t½ 17 h (13–22 h) after patch removal due to skin depot; ~75% excreted in urine (mostly as metabolites, <10% unchanged) | After transdermal patch removal, significant fentanyl continues to be absorbed from the skin depot for 20–27 h — adverse effects persist well after patch removal; in elderly, t½ may extend to ~34 h |
Side Effects
≥10%Very Common
| Adverse Effect | Incidence | Clinical Note |
|---|---|---|
| Nausea | 18% | Prominent during initiation and dose changes; may improve with tolerance development over 3–7 days |
| Constipation | 10–23% | Lower incidence with transdermal vs oral opioids; does not develop tolerance — prophylactic bowel regimen required |
| Somnolence | 10–15% | Dose-related; warn about driving/machinery; often improves within first week of stable dosing |
| Vomiting | 10% | More common during perioperative use and initial transdermal titration; consider anti-emetic prophylaxis |
1–10%Common
| Adverse Effect | Incidence | Clinical Note |
|---|---|---|
| Application site erythema (transdermal patch) | ~8% | Usually mild; resolves within hours of patch removal; rotate application sites; rarely requires discontinuation |
| Headache | 7% | Often self-limiting; assess for medication-overuse headache if persistent |
| Dizziness | 6% | Orthostatic component; advise slow position changes |
| Hyperhidrosis | 5% | Opioid class effect; may persist during chronic use |
| Fatigue / Asthenia | 5% | May reflect dose-related CNS depression; often improves with stable dosing |
| Dry mouth | 4% | Anticholinergic-type effect; encourage oral hydration |
| Insomnia | 4% | May reflect pain control issues or opioid-induced sleep disruption |
| Confusion | 3% | More common in elderly; evaluate for contribution of other CNS depressants |
| Anorexia | 3% | Monitor nutritional status in chronic use; may compound cancer-related cachexia |
| Pruritus | 3% | Less histamine release than morphine; usually non-allergic; responds to antihistamines |
| Bradycardia | <1% | Vagally mediated; more common with high-dose IV use; may require atropine |
SeriousSerious Adverse Effects (Regardless of Frequency)
| Adverse Effect | Estimated Frequency | Typical Onset | Required Action |
|---|---|---|---|
| Respiratory depression / Apnoea | Dose-dependent | Minutes (IV); 24–72 h (transdermal initiation/dose increase) | Hold dosing; naloxone 0.4–2 mg IV q2–3 min (may need repeated doses or infusion as fentanyl effect may outlast naloxone); ventilatory support; remove patch if transdermal |
| Skeletal muscle rigidity (chest wall rigidity) | Uncommon (dose-related; more likely with rapid high-dose IV) | Immediately with IV bolus | Neuromuscular blocking agent (e.g., succinylcholine or rocuronium); secure airway; assisted ventilation |
| Serotonin syndrome | Rare | Hours to days after adding serotonergic co-medication | Discontinue fentanyl and serotonergic agent; supportive care; cyproheptadine may be considered |
| Adrenal insufficiency | Rare | Chronic use (>1 month) | Morning cortisol; if confirmed, physiologic corticosteroid replacement and opioid taper |
| Severe hypotension | Uncommon | After IV bolus or concurrent CNS depressants | IV fluids; vasopressors if refractory; reduce dose; avoid in circulatory shock |
| Seizures | Rare | High-dose use | May be neuroexcitatory phenomenon vs true seizure; benzodiazepines; discontinue fentanyl |
| Androgen deficiency | Unknown (chronic use) | Chronic use (>3 months) | Assess testosterone if symptomatic; endocrinology referral if clinically significant |
| Opioid-induced hyperalgesia (OIH) | Uncommon (chronic use) | Chronic high-dose use | Reduce dose or rotate opioid; paradoxical worsening of pain or pain sensitivity despite increasing doses |
| NOWS (neonatal opioid withdrawal syndrome) | Expected with prolonged maternal use | Within days of delivery | Neonatology team at delivery; neonatal monitoring and scoring; pharmacologic treatment per protocol |
DiscontinuationDiscontinuation Rates
Transdermal RCT (Osteoarthritis, N=216)
~17%
Top reasons: nausea, vomiting, somnolence, dizziness, constipation
Pooled Clinical Trials (N=1,854)
Variable
Top reasons: depression, dizziness, somnolence, headache, nausea, vomiting, constipation, hyperhidrosis, fatigue
| Reason for Discontinuation | Incidence | Context |
|---|---|---|
| Nausea / Vomiting | ≥1% | Most common GI-related reason; typically during initial titration |
| Somnolence / Dizziness | ≥1% | CNS effects; more common in elderly and with concurrent sedatives |
| Constipation | ≥1% | Often preventable with prophylactic bowel regimen |
| Skin reactions (transdermal) | <1% | Application site erythema, dermatitis; rarely severe enough to stop treatment |
Managing Respiratory Depression After Transdermal Patch Removal
Because fentanyl continues to be absorbed from the skin depot for 20–27 hours or more after patch removal, respiratory depression may persist long after the patch is taken off. When treating transdermal fentanyl overdose with naloxone, repeated doses or a continuous infusion of the antagonist may be necessary. Monitor the patient for at least 24 hours after patch removal. This delayed offset is a key distinction from IV fentanyl and significantly affects emergency management.
Drug Interactions
Fentanyl is metabolised exclusively by CYP3A4, making it highly susceptible to pharmacokinetic drug interactions. This is a critical distinction from morphine and hydromorphone (which undergo glucuronidation). CYP3A4-mediated interactions are addressed in an FDA Boxed Warning. Pharmacodynamic interactions with CNS depressants are also clinically significant.
MajorCYP3A4 Inhibitors (ritonavir, ketoconazole, itraconazole, clarithromycin, nelfinavir, nefazodone, diltiazem, verapamil, grapefruit juice)
MechanismInhibition of fentanyl metabolism via CYP3A4
EffectIncreased fentanyl plasma concentrations; potentially fatal respiratory depression
ManagementAvoid combination if possible; if essential, reduce fentanyl dose and monitor closely for respiratory depression; discontinuation of the CYP3A4 inhibitor with ongoing fentanyl may also require dose adjustment
FDA Boxed WarningMajorCYP3A4 Inducers (rifampin, carbamazepine, phenytoin, phenobarbital, St John’s wort)
MechanismIncreased CYP3A4-mediated fentanyl metabolism
EffectDecreased fentanyl levels; loss of analgesic efficacy; may precipitate withdrawal in dependent patients
ManagementIncrease fentanyl dose if necessary and monitor; when the inducer is discontinued, reduce fentanyl dose to prevent overdose as levels will rise
FDA Boxed WarningMajorBenzodiazepines / CNS Depressants
MechanismAdditive CNS and respiratory depression
EffectProfound sedation, respiratory arrest, coma, and death
ManagementAvoid concurrent use where possible; if essential, use lowest effective doses of both and closely monitor
FDA Boxed WarningMajorMAO Inhibitors
MechanismUnpredictable potentiation of opioid effects
EffectSerotonin syndrome, respiratory depression, hypotension, coma
ManagementAvoid within 14 days of MAOI therapy
FDA PIMajorSerotonergic Drugs (SSRIs, SNRIs, triptans, TCAs)
MechanismAdditive serotonergic activity
EffectSerotonin syndrome: agitation, hyperthermia, clonus, diaphoresis
ManagementMonitor for serotonin syndrome; discontinue fentanyl if suspected
FDA PIMajorMixed Agonist-Antagonist Opioids (buprenorphine, nalbuphine, butorphanol)
MechanismCompetitive antagonism at mu-receptor
EffectReduced analgesic effect; may precipitate acute withdrawal
ManagementAvoid concurrent use
FDA PIModerateGabapentinoids (gabapentin, pregabalin)
MechanismAdditive CNS and respiratory depression
EffectIncreased sedation, respiratory depression
ManagementUse lowest effective doses; monitor respiratory status
FDA PIModerateNeuromuscular Blocking Agents
MechanismAdditive respiratory depression; fentanyl-induced rigidity may complicate NMB assessment
EffectProlonged apnoea; difficulty ventilating
ManagementAnticipated in anaesthetic practice; ensure trained airway management and reversal agents available
FDA PIMinorDiuretics
MechanismOpioid-induced ADH release may reduce diuretic response
EffectDecreased diuretic efficacy
ManagementMonitor fluid balance; adjust diuretic if needed
FDA PIMinorAnticholinergic Agents
MechanismAdditive reduction in GI motility
EffectWorsened constipation, urinary retention, paralytic ileus
ManagementMonitor bowel function; aggressive bowel regimen
LexicompMonitoring
- Respiratory Rate & SpO2Continuously during IV use; first 24–72 h of transdermal initiation/dose change
RoutineTarget respiratory rate ≥12/min. Use capnography during procedural sedation. Respiratory depression may outlast analgesic effect (IV) and persists after patch removal (transdermal). Highest risk during first application and after dose increases. - Pain AssessmentEvery dose change; routine visits
RoutineValidated scales (NRS, VAS, BPI). Functional outcomes should also be documented. Watch for opioid-induced hyperalgesia (worsening pain despite dose escalation). - Bowel FunctionEvery visit
RoutineAssess constipation and adherence to bowel regimen. Lower incidence with transdermal vs oral opioids, but still significant. - Patch Integrity & Application SiteEvery patch change (q72h)
RoutineEnsure patch is adhering properly. Check for skin irritation. Rotate application sites. Verify previous patch is removed before applying new one (double-patching is a common cause of overdose). - Body TemperatureOngoing for transdermal
Trigger-basedFever (≥40°C) or external heat exposure can increase fentanyl absorption by ~33%. Monitor for signs of overdose and reduce dose if necessary. - Aberrant BehaviourBefore initiation and ongoing
RoutineUse validated risk tools (ORT, SOAPP-R). Check PDMP at each visit. Urine drug screening per protocol. Count used patches at returns. - CYP3A4 Medication ReviewAt each visit and new prescription
Trigger-basedCritical interaction pathway. Any addition or removal of a CYP3A4 inhibitor or inducer requires fentanyl dose reassessment. Include OTC medications, herbal supplements, and dietary items (grapefruit). - Endocrine FunctionIf symptomatic
Trigger-basedChronic opioid use can cause HPA axis suppression and hypogonadism. Check morning cortisol and testosterone/LH if symptoms arise.
Contraindications & Cautions
Absolute Contraindications
- Significant respiratory depression in unmonitored settings or without resuscitative equipment
- Acute or severe bronchial asthma in unmonitored environment without resuscitative equipment
- Known or suspected GI obstruction including paralytic ileus (transdermal)
- Opioid-non-tolerant patients (transdermal formulation only)
- Known hypersensitivity to fentanyl or any formulation component
- Concurrent or recent MAOI use (within 14 days)
- Acute or postoperative pain — transdermal patch must never be used for short-term pain
Relative Contraindications (Specialist Input Recommended)
- Severe hepatic impairment — decreased fentanyl clearance expected; transdermal not recommended
- Severe renal impairment — although fentanyl has no active metabolites, clearance may be reduced; transdermal not recommended
- History of substance use disorder — fentanyl has very high abuse potential; structured risk mitigation required
- Head injury or raised intracranial pressure — may obscure neurological assessment; CO2 retention risk
- Pregnancy (prolonged use) — NOWS risk; neonatology involvement required
- Concurrent CYP3A4 inhibitor therapy — risk of fatal accumulation; requires dose reduction and close monitoring
Use with Caution
- Elderly or debilitated patients — increased sensitivity; start at reduced doses
- COPD or cor pulmonale — further depression of respiratory drive
- Hypotension, hypovolaemia, or circulatory shock — fentanyl may exacerbate haemodynamic compromise
- Seizure disorders — fentanyl may lower seizure threshold at high doses
- Fever or conditions causing elevated body temperature — increases transdermal absorption
- Bradyarrhythmias — fentanyl may cause vagally-mediated bradycardia
FDA Boxed Warning
Opioid Analgesic REMS — Addiction, Abuse, Misuse, Respiratory Depression, and CYP3A4 Interactions
Fentanyl exposes users to risks of addiction, abuse, and misuse leading to overdose and death. Serious, life-threatening respiratory depression may occur, especially during initiation or dose increase. Concomitant use with benzodiazepines or other CNS depressants may result in profound sedation, respiratory depression, coma, and death. Concomitant use with CYP3A4 inhibitors (or discontinuation of CYP3A4 inducers) may result in fatal overdose. Accidental exposure, especially in children, can be fatal. Prolonged use during pregnancy causes NOWS. The FDA requires a REMS for all opioid analgesics.
FDA Boxed Warning — Transdermal Patch
Transdermal Fentanyl: Opioid-Tolerant Patients Only; Accidental Exposure
Fentanyl transdermal patches must only be prescribed for opioid-tolerant patients. Accidental exposure to even one used or unused patch, especially by children, can result in fatal respiratory depression. Used patches must be folded adhesive side inward and disposed of properly (flushing or take-back program). Substantial amounts of active fentanyl remain in patches after use.
Patient Counselling
Purpose of Therapy
Fentanyl is a very strong pain medication used for severe pain that has not responded to other treatments. The patch form delivers medication slowly through the skin over three days and is only for patients who are already taking and tolerant to strong opioid painkillers. The goal is to provide steady pain relief while minimising the peaks and troughs associated with taking oral medications multiple times per day.
How to Use (Transdermal Patch)
Apply the patch to a flat, non-irritated, non-irradiated area of intact skin on the upper arm, chest, back, or side. Clean the area with water only (no soaps, oils, or lotions). Press the patch firmly in place for 30 seconds, ensuring good contact especially around the edges. Change the patch every 72 hours (3 days) and apply the new patch to a different location. Remove the old patch before applying the new one. Fold used patches adhesive side inward and dispose of them safely.
Heat Exposure & Fever
Tell patientHeat can cause the patch to release too much medication at once, potentially causing a fatal overdose. Do not expose the patch area to heating pads, electric blankets, heated waterbeds, saunas, hot tubs, sunbathing, or hot baths. If you develop a fever, contact your prescriber as your dose may need adjustment.
Call prescriberIf you develop a fever above 39°C (102°F) or experience excessive drowsiness, confusion, or slow breathing while wearing the patch.
Breathing Difficulties
Tell patientThis medication can slow your breathing, especially during the first 24–72 hours after starting or increasing a dose. Family members or carers should know the signs: unusually slow or shallow breathing, blue lips, extreme drowsiness from which you cannot be woken. Have naloxone (Narcan) available if prescribed.
Call prescriberSeek emergency help immediately for very slow breathing, blue skin, or inability to be roused. Remove the patch while waiting for help.
Safe Storage & Disposal
Tell patientEven used patches contain enough fentanyl to seriously harm or kill a child, pet, or adult who is not opioid-tolerant. Store patches in the original sealed pouch until ready to use. Keep all patches locked away from children. After removal, fold the patch adhesive side inward and flush it down the toilet or take to a DEA take-back location. Never place used patches in household waste.
Call prescriberImmediately contact emergency services if anyone accidentally applies, ingests, or has skin contact with a patch that was not prescribed for them.
Constipation
Tell patientConstipation is a common side effect that does not improve over time. Start the bowel regimen your prescriber recommends from day one. Although constipation may be somewhat less severe with the patch compared to oral opioids, it still requires active management with laxatives, fluids, and dietary fibre.
Call prescriberIf you have not had a bowel movement in 3 or more days, or develop abdominal pain, bloating, or vomiting.
Drowsiness & Driving
Tell patientFentanyl can cause drowsiness, dizziness, and impaired thinking. Do not drive, operate machinery, or make important decisions until you know how this medication affects you. These effects are usually worst during the first few days and may improve as your body adjusts.
Call prescriberIf drowsiness or confusion worsens or interferes with your daily activities after the first week.
Medications & Alcohol
Tell patientDo not drink alcohol while using fentanyl. Many common medications can interact dangerously with fentanyl, including some antibiotics, antifungal drugs, HIV medications, and even grapefruit juice. Always inform all healthcare providers that you are using fentanyl before starting any new medication.
Call prescriberBefore starting any new prescription, over-the-counter medication, or herbal supplement while on fentanyl.
Stopping the Medication
Tell patientDo not suddenly stop using fentanyl patches if you have been using them for more than a few weeks. Abrupt discontinuation can cause withdrawal symptoms including anxiety, muscle aches, sweating, nausea, diarrhoea, and insomnia. Your prescriber will gradually reduce your dose over time.
Call prescriberIf you experience significant withdrawal symptoms during a taper.
Sources
Regulatory (PI / SmPC)
- Fentanyl Citrate Injection — Full prescribing information (Pfizer). FDA/Drugs@FDA. Pfizer LabelingPrimary reference for injectable fentanyl dosing by surgical scenario, PK parameters (Vd, t½, clearance), and muscle rigidity warnings.
- Fentanyl Transdermal System — Full prescribing information. DailyMed. DailyMedSource for transdermal patch dosing, opioid-tolerant definitions, equianalgesic conversion tables, heat exposure warnings, and adverse reaction rates from clinical trials (N=1,854).
- Duragesic (fentanyl transdermal system) — Full prescribing information. FDA/Drugs@FDA. FDA LabelOriginal Duragesic PI with detailed adverse reaction tables from cancer (N=153) and postoperative (N=357) patient populations.
Key Clinical Trials
- Ahmedzai S, Brooks D. Transdermal fentanyl versus sustained-release oral morphine in cancer pain: preference, efficacy, and quality of life. J Pain Symptom Manage. 1997;13(5):254–261. doi:10.1016/S0885-3924(97)00082-1Key RCT comparing transdermal fentanyl with sustained-release oral morphine in cancer pain, demonstrating equivalent efficacy with better patient preference and lower constipation.
- Hadley G, Derry S, Moore RA, Wiffen PJ. Transdermal fentanyl for cancer pain. Cochrane Database Syst Rev. 2013;(10):CD010270. doi:10.1002/14651858.CD010270.pub2Cochrane systematic review summarising evidence for transdermal fentanyl in cancer pain; finds equivalence with oral morphine for analgesic efficacy.
- Peng PW, Sandler AN. A review of the use of fentanyl analgesia in the management of acute pain in adults. Anesthesiology. 1999;90(2):576–599. doi:10.1097/00000542-199902000-00034Comprehensive review of IV fentanyl pharmacology and dosing in acute pain and perioperative settings.
Guidelines
- Dowell D, Ragan KR, Jones CM, Baldwin GT, Chou R. CDC Clinical Practice Guideline for Prescribing Opioids for Pain — United States, 2022. MMWR Recomm Rep. 2022;71(RR-3):1–95. doi:10.15585/mmwr.rr7103a1Current CDC guideline on opioid prescribing; informs risk assessment, monitoring, and dose threshold recommendations.
- Fallon M, Giusti R, Aielli F, et al. Management of cancer pain in adult patients: ESMO Clinical Practice Guidelines. Ann Oncol. 2018;29(Suppl 4):iv166–iv191. doi:10.1093/annonc/mdy152European guideline positioning transdermal fentanyl as an alternative step III opioid in cancer pain management.
- Devlin JW, Skrobik Y, Gélinas C, et al. Clinical Practice Guidelines for the Prevention and Management of Pain, Agitation/Sedation, Delirium, Immobility, and Sleep Disruption in Adult Patients in the ICU. Crit Care Med. 2018;46(9):e825–e873. doi:10.1097/CCM.0000000000003299SCCM PADIS guidelines supporting fentanyl infusion for ICU pain management and sedation.
Mechanistic / Basic Science
- Comer SD, Cahill CM. Fentanyl: receptor pharmacology, abuse potential, and implications for treatment. Neurosci Biobehav Rev. 2019;106:49–57. doi:10.1016/j.neubiorev.2018.12.005Detailed review of fentanyl receptor pharmacology, explaining mu-opioid selectivity and abuse liability mechanisms.
- Nelson L, Schwaner R. Transdermal fentanyl: pharmacology and toxicology. J Med Toxicol. 2009;5(4):230–241. doi:10.1007/BF03178274Covers skin depot pharmacology, delayed offset kinetics, and toxicological considerations unique to transdermal delivery.
Pharmacokinetics / Special Populations
- Ziesenitz VC, Vaughns JD, Koch G, Mikus G, van den Anker JN. Pharmacokinetics of fentanyl and its derivatives in children: a comprehensive review. Clin Pharmacokinet. 2018;57(2):125–149. doi:10.1007/s40262-017-0569-6Comprehensive review of paediatric fentanyl pharmacokinetics including maturational changes in CYP3A4 activity and body composition.
- Ramos-Matos CF, Bistas KG, Lopez-Ojeda W. Fentanyl. In: StatPearls [Internet]. Treasure Island (FL): StatPearls Publishing; 2023 May 29. NCBI BookshelfStatPearls reference covering fentanyl pharmacology, dosing, and monitoring across all formulations and clinical contexts.